Abstract
Transition elements are important alloying elements in aluminum alloys, whilst there was a blank of the role of Ti in cast Al-Li-Cu alloys. In this study, the impact of 0.1 and 0.2 wt% Ti additions on Al-2.5Li-1.5Cu-1Zn-0.5Mg(?0.2Zr) alloys has been investigated by microstructure characterizations and tensile tests. The optical microscopy results showed that the grains were significantly refined as the transition elements presented. There was little poisoning phenomenon in the alloys containing both Zr and Ti for the limited holding time during the smelting process. The age-hardening and mechanical properties were prominently enhanced with the addition of Ti and Zr after ageing at 150 oC. The results of transmission electron microscopy showed that dispersed and dense θ? (Al2Cu) precipitates distributed in the alloy containing 0.2 wt% Ti, while T1 (Al2CuLi) phases dominated in the alloy containing 0.2 wt% Ti and 0.2 wt% Zr, accompanied by a moderate number of S? (Al2CuMg). The coarsening rates of δ?(Al3Li) and δ?-precipitation free zones (PFZs) decreased gradually with the content of transition elements increasing, but the case in the 0Zr2Ti alloy was abnormal for the interaction between θ? and δ?. The best comprehensive mechanical properties of YS = 374 MPa, UTS= 527 MPa and EL = 7.1% could be obtained by 2Zr2Ti alloy after ageing at 150 °C for 64 h.
NSTL
Elsevier